Podcasts aren't just for iPods. A podcast is an audio file that you can listen to on your computer or an mp3 player and you can "subscribe" to these podcasts through an RSS feed or a podcast subscription service, like iTunes. You can find a podcast on nearly anything you can think of. There are some great Professional Development resources that can be found via podcasts. And there are many students creating podcasts in their classrooms from lower school on up.
Professional Development:
EdTechTalk
21st Century Learning
Wesley Fryer
Classroom Podcasts:
Bob Sprankle - Room 208
Community Service Podcasts - Georgetown Day School
2nd Grade Podcasts
Vodcast on Podcasting
Tools for Podcasting:
Odeo Studio
ProfCast
Search for Podcasts:
Education Podcast Network (epn)
iTunes
iPodder